1. Field of the Invention
This invention relates to an information input device for inputting information into an information processing apparatus, and more particularly relates to an information input device for inputting information into an information processing apparatus by means of contacting, for example, a finger or the like to an input surface.
2. Description of the Related Art
As an information input device of this kind, the so-called touch-panel input device comprising an ultrasonic digitizer and so forth is well known. Such a touch-panel device is incorporated in a computer system, or an information processing apparatus in which a computer is utilized, and comprises a transparently-constituted input unit which is used overlapped with a display surface of a display device in the information processing apparatus. While watching a display on the display device or the like through the transparent input unit of the touch panel device, the operator can perform position assignment, coordinate input or the like by means of contacting an instruction means, such as a pen, or a finger or the like to an input surface serving as the input unit of the touch-panel device. In general, the power supply of the touch-panel device is, for example, supplied from the main frame of the information processing apparatus, and is not turned on and off independently in the touch-panel device.
Since, in the touch-panel device, input is performed by means of contacting a pen, a finger or the like to the input surface, stains may adhere to the input surface due to the contact. In order to clean the stains, a touch-panel device has been proposed by the present inventors in U.S. patent application Ser. No. 183,637, filed Apr. 19, 1988, assigned in common with the present application, in which cleaning can be performed under the condition that the power supply of an information input device has been turned on, i.e., under the condition that the input of information is possible.
In this device, an input-disable region is set in the input surface when a cleaning mode has been set. Since input is not affected even when that region on the input surface is contacted by a cloth or the like for the purpose of cleaning, cleaning of the input surface can be performed with turning off the power supply. Further, since the input-disable region can be freely moved on the input picture, cleaning can be performed over the entire input surface.
However, in the picture displayed through this touch-panel device, the background is not very bright, and hence stains on the input surface can not be clearly observed. Consequently, there is the problem that unwiped portions or the like will remain, even when the operator believes the input surface has been wiped.